gcw...I found out that my cylinder is a 3/4..that's what the tech told me.not sure if that tells you anything..but is it ok to use that with the new KWA 6.02 tightbore in 509mm barrel..I will be cutting it down to 455mm though

A picture would be best and we can confirm that for you but if it's a standard SR7 then it's a type 1 cylinder which should work. Personally, I would use a KWA type 0.5 which is good for 395-509+mm but optimized for 425mm.